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On 17/02/2009, at 3:14 AM, Joe Sam Shirah wrote:
Thanks to both you and Simon. I was hoping that there was
something
that would give the base WebSphere activity level or threads given
some
load. Then I could add an educated guess for the number of users.
See the Performance Capabilities Reference--Chapter 6 covers web
server and WebSphere performance. Also mentions the Systems Workload
Estimator but that's usually for sizing an appropriate system rather
than tuning performance on a given system.
I will look into the Web Performance Advisor.
Didn't know about that tool.
I am monitoring the threads entry that QPRFADJ makes. As a
fallback, if
necessary, I will use the value differential when we move WAS from
*BASE.
While I believe Simon's thread/job explanation, I think this is
like some
other areas of the AS/400 in that I'm not sure that's the entire
story. For
example, QPRFADJ currently has things at a little over 300 for *BASE
activity level. The application supports around 2000 users, and
WAS all by
itself runs many threads. I realize the significance of *concurrent*
threads, but still...
It is not necessary to have an activity-level for each active thread--
only for those actually doing work. Inactive threads (i.e. those
waiting for something to happen such as I/O) can be paged out.
Examine the transitions Active->Wait, Wait->Ineligible, and
especially Active->Ineligible.
Also, is all your work occurring in *BASE? If so that's not a good
idea. Better to separate workloads by performance profile (e.g.,
batch, interactive, web, communications, etc.). *BASE should be left
for the subsystem monitor jobs, some IBM jobs, plus as a pool of
available storage for the Performance Adjuster to move storage into
and out of.
If you've already moved workload out of *BASE then that will help
explain the activity-level of 300. Note that the system is very good
at managing main storage, as long as you have sufficient to avoid
thrashing, so it's certainly possible that 2000 users could be
supported by 300 activity-levels but I suspect you have work
occurring in other pools.
Regards,
Simon Coulter.
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